JP2017218525A - Method for producing phosphorylated cellulose fiber and cellulose-containing material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the production efficiency of phosphorylated cellulose fibers.SOLUTION: The present invention relates to a method for producing phosphorylated cellulose fibers including a step for phosphorylating cellulose fibers, where an initial moisture content of a reaction system is less than 40 mass%. The present invention also relates to a cellulose-containing material produced by such a production method and a cellulose-containing material containing fibrous cellulose with a fiber width of 1000 nm or less.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing phosphorylated cellulose fibers and a cellulose-containing material.

  In recent years, materials that use reproducible natural fibers have attracted attention due to the substitution of petroleum resources and the growing environmental awareness. Among natural fibers, fibrous cellulose having a fiber diameter of 10 μm or more and 50 μm or less, in particular, fibrous cellulose (pulp) derived from wood has been widely used mainly as a paper product so far.

  As the fibrous cellulose, fine fibrous cellulose having a fiber diameter of 1 μm or less is also known. The fine fibrous cellulose can be used as a constituent material of a sheet or a composite. It is known that when fine fibrous cellulose is used, the contact point between the fibers is remarkably increased, so that the tensile strength and the like are greatly improved. In addition, the use of fine fibrous cellulose for applications such as thickeners is also being studied.

  Fine fibrous cellulose can be produced by mechanically treating conventional cellulose fibers, but the cellulose fibers are strongly bonded to each other by hydrogen bonding. Therefore, enormous energy is required to obtain fine fibrous cellulose by simply performing mechanical processing.

  In order to produce fine fibrous cellulose with smaller mechanical treatment energy, it is known that it is effective to perform pretreatment such as chemical treatment and biological treatment in combination with mechanical treatment. In particular, when a hydrophilic functional group (for example, a carboxyl group, a cation group, or a phosphate group) is introduced into the hydroxyl group on the cellulose surface by chemical treatment, an electrical repulsion between ions occurs and the ions are hydrated. By doing so, the dispersibility in an aqueous solvent is particularly improved. For this reason, the energy efficiency of refinement | miniaturization becomes high compared with the case where a chemical process is not performed.

  For example, Patent Documents 1 and 2 disclose phosphorylated fine fibrous cellulose in which a phosphate group forms an ester with a hydroxyl group of cellulose, and a method for producing phosphorylated fine fibrous cellulose. In Patent Document 2, it has been studied to perform the phosphorylation reaction step in the presence of urea or to increase the phosphate group introduction amount by performing the phosphorylation reaction step a plurality of times.

International Publication No. 2013/073652 International Publication No. 2014/185505

  The present inventors have studied for the purpose of providing a method for producing phosphorylated cellulose fibers more efficiently.

As a result of intensive studies to solve the above problems, the present inventors have produced phosphorylated cellulose fibers by setting the initial moisture content of the reaction system in the step of phosphorylating cellulose fibers to a predetermined value or less. It has been found that efficiency can be increased.
Specifically, the present invention has the following configuration.

[1] A method for producing a phosphorylated cellulose fiber comprising a step of phosphorylating cellulose fibers, wherein the initial moisture content of the reaction system is less than 40% by mass.
[2] The method for producing phosphorylated cellulose fibers according to [1], wherein the step of phosphorylating includes a step of mixing cellulose fibers, an organic solvent, and a phosphorylating agent.
[3] The organic solvent is dimethylformamide (DMF), dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), aniline, pyridine, quinoline, lutidine, acetonitrile, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), dioxane and The method for producing a phosphorylated cellulose fiber according to [2], comprising at least one selected from urea.
[4] The method for producing a phosphorylated cellulose fiber according to [2] or [3], wherein the phosphorylating agent includes at least one selected from dehydrated condensed phosphoric acid, anhydrous phosphoric acid and phosphoric acid.
[5] The step of phosphorylating includes a step of heating. When heating is performed at 140 ° C. in the heating step, the phosphorylation reaction rate from the start of heating to the elapse of 60 minutes is 0.018 mmol / g. -The manufacturing method of the phosphorylated cellulose fiber in any one of [1]-[4] which is more than min.
[6] The specific viscosity measured according to Tapi T230 of the cellulose-containing material containing the cellulose fiber before undergoing the phosphorylation step is V1, and the cellulose-containing Tappi T230 containing the cellulose fiber obtained in the phosphorylation step is used. The method for producing phosphorylated cellulose fibers according to any one of [1] to [5], in which the value of V2 / V1 is 0.74 or more when the specific viscosity measured according to the above is V2.
[7] The phosphorylation according to any one of [1] to [6], wherein the specific viscosity measured according to Tappi T230 of the cellulose-containing material containing cellulose fibers obtained in the phosphorylation step is 8.0 or more A method for producing cellulose fibers.
[8] A cellulose-containing material containing cellulose fibers having a fiber width of 1000 nm or less, 3 rpm of a slurry obtained by diluting the cellulose-containing material with water so that the solid content concentration is 0.4% by mass, A cellulose-containing material having a viscosity measured by a B-type viscometer at a liquid temperature of 25 ° C. of 14500 mPa · s or more.
[9] A cellulose-containing product containing cellulose fibers having a phosphate group of 0.1 mmol / g or more and having a specific viscosity of 8.0 or more measured according to Tappi T230.
[10] The cellulose-containing product according to [9], wherein the degree of polymerization obtained by measurement according to Tappi T230 is 870 or more.
[11] The cellulose-containing material according to [9] or [10], which contains an organic solvent component.

  According to the production method of the present invention, the production efficiency of phosphorylated cellulose fibers can be increased.

FIG. 1 is a graph showing the relationship between the amount of dropped NaOH and electrical conductivity for a fiber material having a phosphate group.

  Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on representative embodiments and specific examples, but the present invention is not limited to such embodiments.

(Method for producing phosphorylated cellulose fiber)
The present invention relates to a method for producing phosphorylated cellulose fibers including a step of phosphorylating cellulose fibers (hereinafter also referred to as a phosphorylation reaction step). The initial moisture content of the reaction system in the method for producing phosphorylated cellulose fibers of the present invention is less than 40% by mass.

In the present invention, phosphorylated cellulose fibers can be efficiently produced by setting the initial moisture content of the reaction system to less than a predetermined value. In this invention, the energy cost concerning manufacturing a phosphorylated cellulose fiber can be reduced. Moreover, the phosphorylation reaction time in a phosphorylation reaction process can be shortened. Thereby, the production efficiency of phosphorylated cellulose fibers can be increased.
The phosphorylation reaction of cellulose fibers proceeds under conditions where water is not substantially present. However, conventionally, it has been considered that the cellulose fiber solvent in the phosphorylation reaction step is preferably an aqueous solvent in order to increase the solubility of the phosphorylating agent and facilitate uniform dispersion. Therefore, there is a problem that it takes time until the phosphorylation reaction proceeds. In the present invention, by deliberately reducing the initial water content of the solvent in the phosphorylation reaction step, the start point of the phosphorylation reaction of the cellulose fiber is advanced, and further, the phosphate group introduction rate during the phosphorylation reaction is increased. It is a success. In particular, since the rate of the phosphorylation reaction from the start of the phosphorylation reaction to the elapse of a predetermined time can be increased, the time required for the phosphorylation reaction step can be greatly reduced. Thereby, the production efficiency of phosphorylated cellulose fibers can be effectively increased.

  Here, the initial moisture content of the reaction system is the moisture content immediately after mixing the cellulose fiber and the phosphorylating agent necessary for the phosphorylation reaction in the phosphorylation reaction step, and substantially before the phosphorylation reaction starts. Is the water content of the mixture. The initial moisture content of the reaction system can be calculated from the moisture content of various components that are initially mixed in the phosphorylation reaction step. For example, when only cellulose fibers and a phosphorylating agent are mixed in the phosphorylation reaction step, the initial water content of the reaction system can be calculated from the water content of the cellulose fibers and the water content of the phosphorylating agent. . Further, in the phosphorylation reaction step, when the cellulose fiber, the phosphorylating agent, and the solvent are mixed, or when the cellulose fiber is in a slurry form dispersed in the solvent, the moisture content of the cellulose fiber and the phosphorylating agent The initial water content of the reaction system can be calculated from the water content of the solvent and the water content of the solvent. Furthermore, when the cellulose fiber is mixed as a cellulose-containing material containing hemicellulose and the like, the initial moisture content can be obtained by calculating the moisture content of the cellulose-containing material and the moisture content of other components such as a phosphorylating agent. .

  The initial water content of the reaction system may be less than 40% by mass, preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 10% by mass or less. More preferably, it is more preferably at most 3.5% by mass, particularly preferably at most 3.5% by mass, most preferably at most 1% by mass. By setting the initial moisture content of the reaction system within the above range, the phosphate group introduction rate during the phosphorylation reaction can be increased, and the production efficiency of phosphorylated cellulose fibers can be increased.

In this invention, a cellulose fiber can be phosphorylated by performing the phosphorylation reaction of the cellulose containing material containing a cellulose fiber, for example. The cellulose-containing material may be composed of cellulose fibers, but may contain other components such as polysaccharides in which two or more monosaccharides are bonded by glycosidic bonds in addition to cellulose fibers. Examples of monosaccharides include glucose, galactose, mannose, fructose, xylose and the like. Polysaccharides include disaccharides and oligosaccharides in which two of these monosaccharides are bound. Examples of polysaccharides other than cellulose fibers include hydroxyethyl cellulose, methyl hydroxypropyl cellulose, methyl cellulose, carboxymethyl cellulose, hemicellulose, and the like. Moreover, as said other component, components other than polysaccharide derived from raw materials, such as a pulp, may be contained.
In the present embodiment, the cellulose-containing material subjected to the phosphorylation reaction step preferably includes, for example, 75% by mass or more of cellulose fibers, more preferably 80% by mass or more, and further includes 85% by mass or more. preferable. Thereby, it becomes possible to improve the manufacturing efficiency of phosphorylated cellulose fiber more effectively. On the other hand, the upper limit of content of the cellulose fiber contained in a cellulose containing material is not specifically limited, For example, it can be 100 mass%. In addition, as a cellulose containing material, the pulp mentioned later can be mentioned, for example.

  The method for producing phosphorylated cellulose fibers can further include a fibrillation treatment step after the phosphorylation reaction step, for example. By going through such a fibrillation treatment step, the phosphorylated cellulose fiber is refined, and fibrous cellulose (fine fibrous cellulose) having a fiber width of 1000 nm or less can be obtained.

<Phosphorylation reaction process>
The phosphorylation reaction step is a step of introducing a phosphate group or a substituent derived from the phosphate group (sometimes simply referred to as a phosphate group) into the cellulose fiber. The phosphoric acid group is a divalent functional group equivalent to the phosphoric acid obtained by removing the hydroxyl group. Specifically, it is a group represented by —PO ₃ H ₂ . Substituents derived from phosphoric acid groups include substituents such as groups obtained by polycondensation of phosphoric acid groups, salts of phosphoric acid groups, and phosphoric acid ester groups. It may be a group.

In the present invention, the phosphate group or the substituent derived from the phosphate group may be a substituent represented by the following formula (1).

In the formula (1), a, b, m and n each independently represent an integer (where a = b × m); α ⁿ (n is an integer from 1 to n) and α ′ are each independently Represents R or OR. R represents a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, an unsaturated-branched hydrocarbon group. , An aromatic group, or a derivative group thereof; β is a monovalent or higher cation composed of an organic substance or an inorganic substance.

  Although it does not specifically limit as a raw material (henceforth a fiber raw material) of a cellulose fiber, It is preferable to use a pulp from the point of being easy to acquire and cheap. Examples of the pulp include wood pulp, non-wood pulp, and deinked pulp. Examples of wood pulp include hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), dissolved pulp (DP), soda pulp (AP), unbleached kraft pulp (UKP), oxygen bleached craft Chemical pulps such as pulp (OKP) are listed. Moreover, semi-chemical pulps such as semi-chemical pulp (SCP) and chemi-ground wood pulp (CGP), mechanical pulps such as ground wood pulp (GP), thermomechanical pulp (TMP, BCTMP) and the like can be mentioned, but are not particularly limited. Non-wood pulp includes cotton pulp such as cotton linter and cotton lint, non-wood pulp such as hemp, straw and bagasse, cellulose isolated from sea squirts and seaweed, chitin, chitosan, etc., but is not particularly limited. . The deinking pulp includes deinking pulp made from waste paper, but is not particularly limited. The pulp of this embodiment may be used alone or in combination of two or more. Among the above pulps, wood pulp containing cellulose and deinked pulp are preferable in terms of availability. Among wood pulps, chemical pulp is preferable in that it has a large cellulose ratio and is capable of obtaining long fibrous fine fibrous cellulose having a high degree of polymerization. Of these, kraft pulp and sulfite pulp are most preferably selected. When fine fibrous cellulose having a high degree of polymerization is used, high viscosity tends to be obtained.

  In the phosphorylation reaction step, the cellulose fiber is reacted with at least one selected from a compound having a phosphate group and a salt thereof (hereinafter also referred to as “phosphorating agent” or “compound A”). Can do. Such a phosphorylating agent may be mixed in dry or wet cellulose fibers in the form of powder or aqueous solution. As another example, a phosphoric acid powder or an aqueous solution may be added to the cellulose fiber slurry. That is, the phosphorylation reaction step includes at least a step of mixing the cellulose fiber and the phosphorylating agent.

  The phosphorylation reaction step more preferably includes a step of mixing cellulose fibers, a phosphorylating agent, and a solvent. Here, the solvent may be a solvent contained in the cellulose fiber slurry, or may be a solvent added separately from the cellulose fiber or the cellulose fiber slurry. The water content of the solvent is preferably less than 40% by mass, more preferably 30% by mass or less, further preferably 20% by mass or less, and still more preferably 10% by mass or less, The content is particularly preferably 5% by mass or less, more preferably 3.5% by mass or less, and most preferably 1% by mass or less. Especially, it is especially preferable that a solvent is an organic solvent, and it is most preferable that it consists only of an organic solvent.

  The organic solvent used in the phosphorylation reaction step is dimethylformamide (DMF), dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), aniline, pyridine, quinoline, lutidine, acetonitrile, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO). ), At least one selected from dioxane and urea. Among these, the organic solvent is preferably at least one selected from dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and urea. In addition, as an organic solvent, only 1 type of the organic solvent mentioned above may be used, but the organic solvent which mixed 2 or more types may be used. In this case, urea is preferably mixed with the organic solvent. Urea is used as an organic solvent in the phosphorylation reaction step, but may function as a phosphorylating agent described later.

  The phosphorylation reaction step can be performed by reacting a cellulose fiber with a phosphorylating agent. This reaction is performed by the presence of at least one selected from urea and its derivatives (hereinafter also referred to as “compound B”). You may do it below.

  As an example of a method for causing compound A to act on cellulose fibers in the presence of compound B, a method of mixing powder or aqueous solution of compound A and compound B with cellulose fibers in a dry state or a wet state can be mentioned. Another example is a method of adding powders and aqueous solutions of Compound A and Compound B to a slurry of cellulose fibers. Among these, since the uniformity of the reaction is high, a method of adding an aqueous solution of Compound A and Compound B to dry cellulose fibers, or a powder or an aqueous solution of Compound A and Compound B to wet cellulose fibers The method is preferred. Moreover, the compound A and the compound B may be added simultaneously, or may be added separately. Moreover, you may add the compound A and the compound B first used for reaction as aqueous solution, and remove an excess chemical | medical solution by pressing. The form of the cellulose fiber is preferably cotton or thin sheet, but is not particularly limited.

  The phosphorylating agent (compound A) is at least one selected from a compound having a phosphate group and a salt thereof. Examples of the phosphorylating agent include lithium salt of phosphoric acid, sodium salt of phosphoric acid, potassium salt of phosphoric acid, ammonium salt of phosphoric acid, dehydrated condensed phosphoric acid, anhydrous phosphoric acid, phosphoric acid and the like. Among these, the phosphorylating agent is preferably at least one selected from dehydrated condensed phosphoric acid, anhydrous phosphoric acid, and phosphoric acid. In addition, as a phosphoric acid, a thing of various purity can be used, for example, it is possible to use 100% phosphoric acid (normal phosphoric acid) and 85% phosphoric acid. Orthophosphoric acid can be obtained, for example, by reacting diphosphorus pentoxide and phosphoric acid. Specifically, it can be obtained by slowly dropping 85% phosphoric acid with respect to diphosphorus pentoxide in an ice bath. Dehydrated condensed phosphoric acid is obtained by converting phosphoric acid into an inorganic polymer by a dehydration reaction, and examples thereof include pyrophosphoric acid and polyphosphoric acid. Examples of phosphoric anhydride include diphosphorus pentoxide.

  The phosphorylating agent (compound A) is preferably used as an aqueous solution because the uniformity of the reaction is increased and the efficiency of introducing a phosphate group is further increased. The pH of the aqueous solution of the phosphorylating agent (compound A) is not particularly limited, but is preferably 7 or less because the efficiency of introduction of phosphoric acid groups is increased. From the viewpoint of suppressing hydrolysis of pulp fibers, the pH is 3 or more and pH 7 or less. Is more preferable. The pH of the aqueous solution of Compound A may be adjusted by, for example, using a phosphoric acid group-containing compound that exhibits acidity and an alkalinity, and changing the amount ratio thereof. You may adjust pH of the aqueous solution of a phosphorylating agent (compound A) by adding an inorganic alkali or an organic alkali to what shows acidity among the compounds which have a phosphoric acid group.

  The amount of phosphorylating agent (compound A) added to the fiber raw material is not particularly limited, but when the amount of phosphorylating agent (compound A) added is converted to phosphorus atomic weight, the amount of phosphorus atom added to the fiber raw material (absolute dry mass) Is preferably 0.5 to 100% by mass, more preferably 1 to 50% by mass, and most preferably 2 to 30% by mass. If the addition amount of the phosphorus atom with respect to a fiber raw material exists in the said range, the yield of a phosphorylated cellulose fiber can be improved more. By making the amount of phosphorus atoms added to the fiber raw material 100% by mass or less, the effect of improving the yield and the cost can be balanced. On the other hand, a yield can be raised by making the addition amount of the phosphorus atom with respect to a fiber raw material more than the said lower limit.

  Examples of the compound B used in this embodiment include urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, 1-ethylurea and the like.

  Compound B is preferably used as an aqueous solution in the same manner as Compound A. Moreover, since the uniformity of reaction increases, it is preferable to use the aqueous solution in which both compound A and compound B are dissolved. The amount of Compound B added to the fiber raw material (absolute dry mass) is preferably 1% by mass or more and 500% by mass or less, more preferably 10% by mass or more and 400% by mass or less, and 100% by mass or more and 350% by mass or less. More preferably, it is more preferably 150% by mass or more and 300% by mass or less.

  In addition to Compound A and Compound B, amides or amines may be included in the reaction system. Examples of amides include formamide, dimethylformamide, acetamide, dimethylacetamide and the like. Examples of amines include methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine, and the like. Among these, triethylamine is known to work as a good reaction catalyst.

  In the present embodiment, for example, the phosphorylation reaction step may be a step of phosphorylating a cellulose-containing material including cellulose fibers. In this case, the phosphorylation reaction step includes, for example, a step of mixing the cellulose-containing material, the solvent, the compound A, and, if necessary, the compound B. In addition, as a cellulose containing material, it is possible to use the fiber raw material illustrated above, for example.

  The phosphorylation reaction step preferably further includes a step of heating (hereinafter also referred to as a heat treatment step). As the heat treatment temperature in the heat treatment step, it is preferable to select a temperature at which phosphate groups can be efficiently introduced while suppressing thermal decomposition and hydrolysis reaction of cellulose fibers. Specifically, it is preferably 50 ° C. or higher and 300 ° C. or lower, more preferably 100 ° C. or higher and 250 ° C. or lower, and further preferably 130 ° C. or higher and 200 ° C. or lower. Moreover, you may use a vacuum dryer, an infrared heating apparatus, and a microwave heating apparatus for a heating.

  During the heat treatment, while the cellulose fiber slurry to which the compound A is added contains water, if the time for allowing the cellulose fiber to stand still becomes long, the compound A dissolved with water molecules moves to the fiber raw material surface with drying. To do. Therefore, the concentration of the compound A in the fiber raw material may be uneven, and the introduction of phosphate groups on the fiber surface may not proceed uniformly. In order to suppress the occurrence of unevenness in concentration of Compound A in the fiber material due to drying, a very thin sheet-like fiber material is used, or the fiber material and Compound A are kneaded or stirred with a kneader or the like and dried by heating or reduced pressure. The method should be taken.

  The heating device used for the heat treatment is preferably a device that can always discharge the moisture retained by the slurry and the moisture generated by the addition reaction of the fibers such as phosphate groups to the hydroxyl group of the fiber, such as a blower oven. Etc. are preferred. If water in the system is always discharged, the hydrolysis reaction of the phosphate ester bond, which is the reverse reaction of the esterification, can be suppressed, and the acid hydrolysis of the sugar chain in the fiber can also be suppressed. A fine fiber having a high degree of polymerization can be obtained.

  The heat treatment time is also affected by the heating temperature, but it is preferably 1 second or more and 300 minutes or less, and more preferably 1 second or more and 60 minutes or less after the moisture is substantially removed from the fiber raw material slurry. Preferably, it is 10 seconds or more and 1500 seconds or less. In the present invention, the amount of phosphate groups introduced can be within a preferred range by setting the heating temperature and the heating time to appropriate ranges.

  The amount of phosphate group introduced into the cellulose fiber is preferably 0.1 mmol / g or more and 3.65 mmol / g or less, more preferably 0.14 mmol / g or more and 3.5 mmol / g or less, and 0.2 mmol / g or less. g to 3.2 mmol / g is more preferable, 0.4 mmol / g to 3.0 mmol / g is particularly preferable, and 0.6 mmol / g to 2.5 mmol / g is most preferable. By making the introduction amount of the phosphoric acid group within the above range, it is possible to facilitate the refinement of the cellulose fiber and enhance the stability of the fine fibrous cellulose when the phosphorylated cellulose fiber is subjected to a defibrating treatment.

  The amount of phosphate groups introduced into the cellulose fiber can be measured by a conductivity titration method. Specifically, after the slurry obtained after the phosphorylation reaction step is treated with an ion exchange resin, the amount of introduction can be measured by obtaining a change in electrical conductivity while adding an aqueous sodium hydroxide solution. In addition, you may perform the said measurement using the phosphorylated cellulose fiber which performed the defibrating process. When the method for producing a phosphorylated cellulose fiber of the present invention includes a defibrating treatment step, the amount of phosphate groups introduced may be measured using the slurry obtained after the defibrating treatment step. When the manufacturing method does not include a defibrating process, the defibrating process may be performed before the measurement.

  In conductivity titration, when alkali is added, the curve shown in FIG. 1 is given. Initially, the electrical conductivity rapidly decreases (hereinafter referred to as “first region”). Thereafter, the conductivity starts to increase slightly (hereinafter referred to as “second region”). Thereafter, the conductivity increment increases (hereinafter referred to as “third region”). That is, three areas appear. Among these, the amount of alkali required in the first region is equal to the amount of strongly acidic groups in the slurry used for titration, and the amount of alkali required in the second region is the amount of weakly acidic groups in the slurry used for titration. Will be equal. When the phosphoric acid group undergoes condensation, apparently weakly acidic groups are lost, and the amount of alkali required in the second region is reduced compared to the amount of alkali required in the first region. On the other hand, the amount of strongly acidic groups coincides with the amount of phosphorus atoms regardless of the presence or absence of condensation, so that the amount of phosphate groups introduced (or the amount of phosphate groups) or the amount of substituent introduced (or the amount of substituents) is simply When said, it represents the amount of strongly acidic group. That is, the alkali amount (mmol) required in the first region of the curve shown in FIG. 1 is divided by the solid content (g) in the titration target slurry to obtain the substituent introduction amount (mmol / g).

  The method for producing phosphorylated cellulose fibers of the present invention is also characterized in that the phosphorylation reaction rate is high in the heat treatment step. For example, in the heat treatment step, when heating is performed at 140 ° C., the phosphorylation reaction rate from the start of heating to the elapse of 60 minutes is preferably 0.018 mmol / g · min or more, and 0.020 mmol / More preferably, it is g · min or more, and further preferably 0.022 mmol / g · min or more. In the present invention, the initial phosphorylation reaction rate from the start of heating to the elapse of a predetermined time is sufficiently high, thereby increasing the energy efficiency in the production process of phosphorylated cellulose fibers.

  In the heat treatment step, when heating is performed at 140 ° C., the phosphorylation reaction rate from the start of heating to the elapse of 60 minutes can be calculated by the following method. First, the amount of phosphate group introduced at each time of 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, and 60 minutes after the start of heating by the method described above. taking measurement. Next, the vertical axis is the phosphate group introduction amount (mmol / g), the horizontal axis is the reaction time (min), and the obtained data is plotted on a graph. An approximate line is created from the plotted graph, and the slope of the approximate line is defined as a reaction rate a (mmol / g · min).

  Cellulose-containing material containing cellulose fibers obtained in the phosphorylation reaction step (hereinafter referred to as phosphorylated cellulose-containing material), where V1 is the specific viscosity measured according to Tappi T230 of the cellulose-containing material containing cellulose fibers before undergoing the phosphorylation reaction step When the specific viscosity measured according to Tappi T230 is V2, the value of V2 / V1 is preferably 0.74 or more, more preferably 0.80 or more, and 0.81 More preferably, it is the above. Moreover, it is preferable that the value of V2 / V1 is 1.5 or less. The present invention is characterized in that there is little decrease in the specific viscosity of the phosphorylated cellulose-containing material even after the phosphorylation reaction step, and the cellulose-containing material thus obtained exhibits excellent thickening properties. Can do. The cellulose-containing material preferably contains, for example, 75% by mass or more of cellulose fiber, more preferably 80% by mass or more, and further preferably 85% by mass or more. The cellulose-containing material may be composed of cellulose fibers or may contain other components such as the polysaccharides described above.

The specific viscosity of the cellulose-containing material and the phosphorylated cellulose-containing material can be measured by the following method according to Tappi T230. First, the viscosity of a slurry in which a cellulose-containing material before phosphorylation or a phosphorylated cellulose-containing material is dispersed in a dispersion medium (referred to as η ₁ ) and a blank viscosity (referred to as η ₀ ) measured using only the dispersion medium are measured. To do. Thereafter, the specific viscosity (η _sp ) and the intrinsic viscosity ([η]) are calculated according to the following formula.
η _sp = (η ₁ / η ₀ ) -1
[Η] = η _sp /(c(1+0.28×η _sp ))
Here, c in a formula shows the density | concentration of the cellulose containing material or phosphorylated cellulose containing material at the time of a viscosity measurement.

  The specific viscosity of the cellulose-containing material before phosphorylation is preferably 8.0 or more, more preferably 9.0 or more, and further preferably 10.0 or more. Further, the specific viscosity of the phosphorylated cellulose-containing material is preferably 8.0 or more, more preferably 8.5 or more, and further preferably 8.8 or more.

  When the degree of polymerization of the cellulose-containing material before passing through the phosphorylation reaction step is DPa and the degree of polymerization of the phosphorylated cellulose-containing material obtained in the phosphorylation reaction step is DPb, the DPb / DPa value is 0.92 or more. Preferably, it is 0.93 or more, more preferably 0.94 or more. Moreover, it is preferable that the value of DPb / DPa is 1.5 or less. The present invention is characterized in that the decrease in the degree of polymerization of the phosphorylated cellulose-containing product through the phosphorylation reaction step is small. This is presumed to be because hydrolysis of the cellulose-containing material is suppressed in the phosphorylation reaction step.

The degree of polymerization of the cellulose-containing material and the phosphorylated cellulose-containing material can be measured according to Tappi T230. First, specific viscosity (η _sp ) and intrinsic viscosity ([η]) are calculated by the method described above. Then, the degree of polymerization (DP) is calculated from the following formula.
DP = 1.75 × [η]
Such a degree of polymerization is an average degree of polymerization measured by a viscosity method, and is sometimes referred to as “viscosity average degree of polymerization”.

  The degree of polymerization of the cellulose-containing material before phosphorylation is preferably 500 or more, more preferably 600 or more, further preferably 800 or more, and particularly preferably 900 or more. The degree of polymerization of the phosphorylated cellulose-containing material is preferably 500 or more, more preferably 600 or more, further preferably 800 or more, and particularly preferably 870 or more.

  The phosphorylation reaction step as described above may be performed at least once, but may be repeated a plurality of times. In the present invention, since the phosphorylation reaction rate is high and the phosphorylation efficiency is increased, the number of steps of the phosphorylation reaction step can be reduced. For example, the number of steps of the phosphorylation reaction step is preferably 1 or more and 3 or less, and may be once. In the present invention, a sufficient amount of phosphoric acid groups can be introduced into the cellulose fiber even when the number of phosphorylation reaction steps is small.

<Alkali treatment process>
The manufacturing method of the phosphorylated cellulose fiber of this invention includes a phosphorylation reaction process, and can further include a fibrillation process process. When the manufacturing method of a phosphorylated cellulose fiber includes a fibrillation treatment step, it is preferable to provide an alkali treatment step between the phosphorylation reaction step and the fibrillation treatment step described later. Although it does not specifically limit as a method of an alkali treatment, For example, the method of immersing a phosphorylated cellulose fiber in an alkaline solution is mentioned. In addition, the phosphorylated cellulose containing material obtained by the phosphorylation reaction process may be used for the said alkali treatment.

  The alkali compound contained in the alkali solution is not particularly limited, but may be an inorganic alkali compound or an organic alkali compound. The solvent in the alkaline solution may be either water or an organic solvent. The solvent is preferably a polar solvent (polar organic solvent such as water or alcohol), and may be an aqueous solvent. Of the alkaline solutions, a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution is particularly preferred because of its high versatility.

Although the temperature of the alkali solution in an alkali treatment process is not specifically limited, 5 to 80 degreeC is preferable and 10 to 60 degreeC is more preferable.
The immersion time in the alkaline solution in the alkali treatment step is not particularly limited, but is preferably 5 minutes or longer and 30 minutes or shorter, and more preferably 10 minutes or longer and 20 minutes or shorter.
Although the usage-amount of the alkali solution in an alkali treatment is not specifically limited, It is preferable that it is 100 mass% or more and 100,000 mass% or less with respect to the absolute dry mass of a phosphorylated cellulose fiber, and it is 1000 mass% or more and 10000 mass% or less. Is more preferable.

  In order to reduce the amount of alkaline solution used in the alkali treatment step, the phosphorylated cellulose fiber may be washed with water or an organic solvent before the alkali treatment step. After the alkali treatment, in order to improve handling, it is preferable to wash the alkali-treated phosphorylated cellulose fiber with water or an organic solvent before the defibrating treatment step.

<Acid treatment process>
When the manufacturing method of the phosphorylated cellulose fiber of this invention includes a fibrillation treatment process, you may provide an acid treatment process between a phosphorylation reaction process and the fibrillation treatment process mentioned later. Moreover, you may perform a phosphorylation reaction process, an acid treatment, an alkali treatment, and a defibration process in this order.

  Although it does not specifically limit as a method of an acid treatment, For example, the method of immersing a phosphorylated cellulose fiber in the acidic liquid containing an acid is mentioned. Although the density | concentration of the acidic liquid to be used is not specifically limited, 10 mass% or less is preferable, More preferably, it is 5 mass% or less. As the acid contained in the acidic liquid, for example, an inorganic acid, a sulfonic acid, a carboxylic acid, or the like can be used. Examples of the inorganic acid include sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, phosphoric acid, boric acid and the like. Examples of the sulfonic acid include methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid, and the like. Examples of the carboxylic acid include formic acid, acetic acid, citric acid, gluconic acid, lactic acid, oxalic acid, and tartaric acid. Of these, hydrochloric acid is preferably used as the acid. Moreover, the phosphorylated cellulose containing material obtained by the phosphorylation reaction process may be used for the said acid treatment.

Although the temperature of the acid solution in an acid treatment process is not specifically limited, 5 to 80 degreeC is preferable and 10 to 60 degreeC is more preferable.
Although the immersion time in the acid solution in an acid treatment process is not specifically limited, 5 minutes or more and 30 minutes or less are preferable, and 10 minutes or more and 20 minutes or less are more preferable.
Although the usage-amount of the acid solution in an acid treatment is not specifically limited, It is preferable that it is 100 mass% or more and 100,000 mass% or less with respect to the absolute dry mass of a phosphorylated cellulose fiber, and it is 1000 mass% or more and 10000 mass% or less. Is more preferable.

<Defibration process>
The phosphorylated cellulose fiber may be defibrated, for example, in a defibrating process. In the defibrating process, the fiber is usually defibrated using a defibrating apparatus to obtain a fine fibrous cellulose-containing slurry, but the processing apparatus and the processing method are not particularly limited. In addition, the phosphorylated cellulose containing material obtained by the phosphorylation reaction process may be used for the said fibrillation process.

  As the defibrating apparatus, a high-speed defibrator, a grinder (stone mill type pulverizer), a high-pressure homogenizer, an ultra-high pressure homogenizer, a high-pressure collision type pulverizer, a ball mill, a bead mill, or the like can be used. Alternatively, as a defibrating apparatus, a device for wet grinding such as a disk type refiner, a conical refiner, a twin-screw kneader, a vibration mill, a homomixer under high-speed rotation, an ultrasonic disperser, or a beater should be used. You can also. The defibrating apparatus is not limited to the above. Preferable defibrating treatment methods include a high-speed defibrator, a high-pressure homogenizer, and an ultra-high pressure homogenizer that are less affected by the grinding media and less worried about contamination.

  In the defibrating treatment, it is preferable to dilute phosphorylated cellulose or a phosphorylated cellulose-containing material with water and an organic solvent alone or in combination to form a slurry, but there is no particular limitation. As the dispersion medium, a polar organic solvent can be used in addition to water. Preferable polar organic solvents include alcohols, ketones, ethers, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc) and the like, but are not particularly limited. Examples of alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, and t-butyl alcohol. Examples of ketones include acetone and methyl ethyl ketone (MEK). Examples of ethers include diethyl ether and tetrahydrofuran (THF). The dispersion medium may be one type or two or more types. The dispersion medium may contain phosphorylated cellulose or a solid content other than the phosphorylated cellulose-containing material, such as urea having hydrogen bonding properties.

  In the present invention, defibrating treatment may be performed after the phosphorylated cellulose fiber is concentrated and dried. In this case, the concentration and drying methods are not particularly limited, and examples thereof include a method of adding a concentrating agent to a slurry containing phosphorylated cellulose fibers, a generally used dehydrator, a press, and a method using a dryer. Moreover, a well-known method, for example, the method described in WO2014 / 024876, WO2012 / 107642, and WO2013 / 121086 can be used. Further, the concentrated phosphorylated cellulose fiber may be formed into a sheet. The sheet can be pulverized to perform a defibrating process.

  Equipment used for pulverization of phosphorylated cellulose fibers includes high-speed defibrator, grinder (stone mill type pulverizer), high-pressure homogenizer, ultra-high pressure homogenizer, high-pressure collision type pulverizer, ball mill, bead mill, disk type refiner, conical An apparatus for wet pulverization such as a refiner, a twin-screw kneader, a vibration mill, a homomixer under high-speed rotation, an ultrasonic disperser, a beater, and the like can be used, but is not particularly limited. The treatment conditions are not particularly limited as long as a preferable degree of polymerization is obtained.

  In this invention, it becomes easy to control the average degree of polymerization of a phosphorylated cellulose fiber within a preferable range by appropriately selecting the raw material and production conditions of the phosphorylated cellulose fiber. Such production conditions are not particularly limited. For example, the conditions in the phosphate group introduction step are adjusted, the defibration treatment conditions in the defibration treatment step are adjusted, and the type of the production apparatus is selected. Etc. For example, when using a defibrating apparatus (Cleamix-2.2S, manufactured by M Technique Co., Ltd.), defibrating treatment may be performed for 10 minutes or more and 60 minutes or less under conditions of 10,000 rotations / minute or more and 21500 rotations / minute or less. preferable.

(Cellulose-containing material)
<Cellulose-containing material containing fine fibrous cellulose>
The present invention also relates to a cellulose-containing material containing fine fibrous cellulose. Here, the viscosity measured by a B-type viscometer of the slurry obtained by diluting the cellulose-containing material with water so that the solid content concentration is 0.4% by mass under conditions of 3 rpm and a liquid temperature of 25 ° C. is 14500 mPa · s or more. The viscosity measurement time is 3 minutes. The viscosity of the slurry is more preferably 15000 mPa · s or more, and further preferably 15500 mPa · s or more. The upper limit of the viscosity of the slurry is not particularly limited, but can be set to, for example, 40000 mPa · s. In addition, as above-mentioned, other components, such as hemicellulose, may be contained in the cellulose containing material, for example, and it does not need to be contained.

As a method for adjusting the viscosity of the slurry obtained by diluting a cellulose-containing material containing fine fibrous cellulose with water so that the solid content concentration becomes 0.4 mass%, for example, phosphorous is added to fine fibrous cellulose. Introducing acid groups. That is, the cellulose-containing material of the present invention preferably includes cellulose fibers having a phosphate group-containing fiber width of 1000 nm or less.
In the present embodiment, as described above, for example, a defibrating step can be performed on a cellulose-containing material including phosphorylated cellulose fibers. Thereby, the cellulose containing material containing the cellulose fiber (microfibrous cellulose) whose fiber width by which the phosphorylated cellulose fiber was refined | miniaturized is 1000 nm or less will be obtained. The amount of phosphate groups in cellulose fibers having a phosphate group-containing fiber width of 1000 nm or less is preferably 0.1 mmol / g or more.

  The average fiber width of the fine fibrous cellulose is 1000 nm or less as observed with an electron microscope. The average fiber width is preferably not less than 2 nm and not more than 1000 nm, more preferably not less than 2 nm and not more than 100 nm, still more preferably not less than 2 nm and not more than 50 nm, and still more preferably not less than 2 nm and not more than 10 nm. When the average fiber width of the fine fibrous cellulose is less than 2 nm, the physical properties (strength, rigidity, dimensional stability) as the fine fibrous cellulose tend to be difficult to be expressed because the cellulose molecules are dissolved in water. . The fine fibrous cellulose is monofilamentous cellulose having a fiber width of 1000 nm or less, for example.

  Measurement of the fiber width of the fine fibrous cellulose by electron microscope observation is performed as follows. An aqueous suspension of fine fibrous cellulose having a concentration of 0.05% by mass or more and 0.1% by mass or less is prepared, and the suspension is cast on a carbon film-coated grid subjected to a hydrophilic treatment to prepare a sample for TEM observation. To do. When a wide fiber is included, an SEM image of the surface cast on glass may be observed. Observation with an electron microscope image is performed at a magnification of 1000 times, 5000 times, 10000 times, or 50000 times depending on the width of the constituent fibers. However, the sample, observation conditions, and magnification are adjusted to satisfy the following conditions.

(1) One straight line X is drawn at an arbitrary location in the observation image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y perpendicular to the straight line is drawn in the same image, and 20 or more fibers intersect the straight line Y.

  The width of the fiber that intersects with the straight line X and the straight line Y is visually read from the observation image that satisfies the above conditions. In this way, at least three sets of images of the surface portion that do not overlap each other are observed, and the width of the fiber intersecting with the straight line X and the straight line Y is read for each image. Thus, at least 20 × 2 × 3 = 120 fiber widths are read. The average fiber width (sometimes simply referred to as “fiber width”) of fine fibrous cellulose is an average value of the fiber widths read in this way.

  The fiber length of the fine fibrous cellulose is not particularly limited, but is preferably 0.1 μm or more and 1000 μm or less, more preferably 0.1 μm or more and 800 μm or less, and particularly preferably 0.1 μm or more and 600 μm or less. By making the fiber length within the above range, the destruction of the crystalline region of the fine fibrous cellulose can be suppressed, and the slurry viscosity of the fine fibrous cellulose can be made an appropriate range. Note that the fiber length of the fine fibrous cellulose can be determined by image analysis using TEM, SEM, or AFM.

  The fine fibrous cellulose preferably has an I-type crystal structure. Here, the fact that the fine fibrous cellulose has a type I crystal structure can be identified in a diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ = 1.5418Å) monochromatized with graphite. Specifically, it can be identified by having typical peaks at two positions of 2θ = 14 ° to 17 ° and 2θ = 22 ° to 23 °.

  The ratio (crystallinity) of the I-type crystal structure in the fine fibrous cellulose is not particularly limited in the present invention, but is preferably 30% or more, more preferably 50% or more, and still more preferably 70%. That's it. In this case, further superior performance can be expected in terms of heat resistance and low linear thermal expansion coefficient. The degree of crystallinity is obtained by measuring an X-ray diffraction profile and determining the crystallinity by a conventional method (Seagal et al., Textile Research Journal, 29, 786, 1959).

  The amount of phosphate groups introduced into the fine fibrous cellulose is preferably 0.1 mmol / g or more and 3.65 mmol / g or less, more preferably 0.14 mmol / g or more and 3.5 mmol / g or less, and It is more preferably 2 mmol / g or more and 3.2 mmol / g or less, particularly preferably 0.4 mmol / g or more and 3.0 mmol / g or less, and most preferably 0.6 mmol / g or more and 2.5 mmol / g or less. By making the introduction amount of the phosphoric acid group within the above range, for example, when used as a thickener, good thickening properties can be exhibited. The amount of phosphate groups introduced into the fine fibrous cellulose can be measured, for example, in the same manner as the amount of phosphate groups introduced into the cellulose fibers described above.

  Further, the cellulose-containing material containing fine fibrous cellulose may contain, for example, an organic solvent component. This organic solvent component is derived from the organic solvent mixed in the reaction system when phosphorylating the cellulose-containing material. In the method for producing phosphorylated cellulose fiber of the present invention, an organic solvent is preferably used in the phosphorylation reaction step, and a part of the organic solvent may be detected from a cellulose-containing product as a final product. is there.

<Cellulose-containing material including cellulose fiber>
In the present specification, the cellulose fiber includes fine fibrous cellulose and fibrous cellulose having a fiber width larger than 1000 nm. The present invention may relate to a cellulose-containing material containing cellulose fibers. That is, the present invention may relate to a cellulose-containing material containing cellulose fibers that have not been refined. Such a cellulose-containing material preferably contains cellulose fibers having a phosphate group of 0.1 mmol / g or more, and the specific viscosity measured according to Tappi T230 of the cellulose-containing material is preferably 8.0 or more. . The specific viscosity is more preferably 9.0 or more, and further preferably 10.0 or more. In addition, the specific viscosity of the cellulose containing material containing a cellulose fiber can be measured by the method mentioned above according to Tappi T230.

  It is preferable that the polymerization degree obtained by measuring according to Tappi T230 of a cellulose-containing material containing cellulose fibers is 870 or more. The degree of polymerization of the cellulose-containing material can be calculated by the method described above according to Tappi T230.

  The cellulose-containing material containing cellulose fibers may contain, for example, an organic solvent component. This organic solvent component is derived from the organic solvent mixed in the reaction system when phosphorylating the cellulose-containing material.

(Fine fibrous cellulose-containing slurry)
The present invention may relate to a fine fibrous cellulose-containing slurry. Since the fine fibrous cellulose-containing slurry contains the above-described fine fibrous cellulose, it can exhibit high viscosity and has high transparency.

  The viscosity of the slurry sample obtained by diluting the fine fibrous cellulose-containing slurry with water to a solid content concentration of 0.4% by mass is preferably 14500 mPa · s or more, and preferably 15000 mPa · s or more. More preferably, it is more preferably 15500 mPa · s or more. The upper limit of the viscosity of the slurry sample is not particularly limited, but can be set to, for example, 40000 mPa · s.

  The viscosity of the slurry sample obtained by diluting the fine fibrous cellulose-containing slurry with water to a solid content concentration of 0.4% by mass is measured using a B-type viscometer (manufactured by BLOOKFIELD, analog viscometer T-LVT). Can be measured. The measurement conditions are a liquid temperature of 25 ° C., a rotation speed of 3 rpm, and a measurement time of 3 minutes.

The haze of the fine fibrous cellulose-containing slurry (concentration of fine fibrous cellulose of 0.2% by mass) is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less. . That the haze of the fine fibrous cellulose-containing slurry is in the above range means that the fine fibrous cellulose-containing slurry has high transparency, and the fine fibrous cellulose is finely refined. In such a fine fibrous cellulose-containing slurry, a specific function of the fine fibrous cellulose is exhibited.
Here, the haze of the slurry containing fine fibrous cellulose (fine fibrous cellulose concentration: 0.2% by mass) is applied to a liquid glass cell having a 1 cm optical path length (MG-40, manufactured by Fujiwara Seisakusho, reverse optical path). It is a value measured by using a haze meter (manufactured by Murakami Color Research Laboratory Co., Ltd., HM-150) in accordance with JIS K 7136. The zero point measurement is performed with ion-exchanged water placed in the glass cell.

(Use)
The fine fibrous cellulose produced by the method for producing phosphorylated cellulose fibers of the present invention is suitable for use in light-transmitting substrates such as various display devices and various solar cells. It is also suitable for applications such as substrates for electronic devices, members of household appliances, various vehicles and building windows, interior materials, exterior materials, packaging materials, and the like. Furthermore, it is also suitable for applications in which the sheet itself is used as a reinforcing material in addition to threads, filters, fabrics, cushioning materials, sponges, abrasives, and the like.
Moreover, the viscosity of the fine fibrous cellulose-containing slurry is high, and from the viewpoint of utilizing such characteristics, the fibrous cellulose of the present invention is used as a thickener in various applications (for example, foods, cosmetics, cements, paints, inks, etc.). And the like can be used.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

<Method for measuring solid content concentration of pulp>
A pulp sheet or 2 g of a raw material obtained by fluffing a pulp sheet was placed in a weighing bottle with a known mass, and dried for 16 hours with a dryer (Yamato Kagaku, blast low-temperature dryer DK600). After drying, the container was covered in a drier, placed in a desiccator and allowed to cool. After standing to cool, in order to remove the pressure difference between the inside and outside of the container, the cover of the container was opened half way, quickly closed again, and the mass after drying was measured. The solid content concentration of the pulp was calculated from the following formula (1) using the measured weight.
W _dm = m ₁ ÷ m ₀ × 100 (1)
W _dm : Absolute dry rate (%) expressed as mass fraction
m ₀ : mass before drying (g)
m ₁ : Mass after drying to constant weight (g)

<Method of adjusting regular phosphoric acid>
In an ice bath, 254 parts by mass of 85% phosphoric acid (manufactured by Kanto Chemical Co.) was slowly added dropwise to 100 parts by mass of diphosphorus pentoxide (manufactured by Kanto Chemical Co., Ltd.) to prepare normal phosphoric acid.

<Phosphorylation reaction process>
(Example A-1)
As a cellulose-containing material, a pulp sheet made of Oji Paper (solid content: 93% by mass, basis weight of 208 g / m ² sheet, Canadian standard freeness (CSF) 700 ml which is disaggregated and measured according to JIS P 8121) Used as raw material. To 100 parts by mass of pulp sheet (absolute dry mass), 32 parts by mass of normal phosphoric acid, 100 parts by mass of urea (manufactured by Kanto Chemical Co., Inc.), and 150 parts by mass of N, N-dimethylformamide (DMF) (manufactured by Kanto Chemical Co., Inc.) are added. Then, heat-drying was performed at 140 ° C. for 30 minutes with an explosion-proof dryer (SPH-200, manufactured by ESPEC), and phosphoric acid groups were introduced into the cellulose fibers in the pulp to obtain a phosphorylated cellulose-containing product A.

<Washing and alkali treatment process>
Ion exchanged water was poured into the obtained phosphorylated cellulose-containing product A, and the mixture was stirred and dispersed uniformly, and then the operation of obtaining a dehydrated sheet by filtration and dehydration was repeated to sufficiently wash away excess chemical solution. Subsequently, 1N sodium hydroxide aqueous solution was added little by little, stirring with ion-exchange water so that a cellulose content concentration might be 2 mass%, and the pulp slurry whose pH is 12 +/- 0.2 was obtained. Then, after dehydrating this pulp slurry and obtaining a dehydrated sheet, after adding ion-exchanged water again, stirring and uniformly dispersing, and repeating the operation of obtaining a dehydrated sheet by filtration and dewatering, excess water is obtained. Sodium oxide was thoroughly washed away to obtain phosphorylated cellulose-containing product B.

<Machine processing>
Ion exchange water was added to the obtained phosphorylated cellulose-containing product B to obtain a suspension having a solid content concentration of 0.5% by mass. This suspension was defibrated for 30 minutes using a defibrating apparatus (Cleamix-2.2S, manufactured by M Technique Co., Ltd.) at 21500 rpm, and defibrated pulp slurry (fine fiber form) A cellulose-containing slurry) was obtained.

(Example A-2)
A defibrated pulp slurry (fine fibrous cellulose-containing slurry) was obtained in the same manner as in Example A-1, except that 300 parts by mass of urea was used instead of 150 parts by mass of N, N-dimethylformamide.

(Example A-3)
A defibrated pulp slurry (a slurry containing fine fibrous cellulose) in the same manner as in Example A-1, except that 38 parts by mass of 85% phosphoric acid (manufactured by Kanto Chemical Co., Inc.) was used instead of 32 parts by mass of regular phosphoric acid. )

(Comparative Example A-1)
In the same manner as in Example A-1, except that 150 parts by mass of ion-exchanged water was used instead of 150 parts by mass of N, N-dimethylformamide and the heating and drying time was set to 50 minutes, a defibrated pulp slurry (fine fiber form) A cellulose-containing slurry) was obtained.

(Evaluation)
<Measurement of introduction amount of phosphate group (phosphate group amount)>
The amount of phosphate group introduced was measured by a conductivity titration method. Specifically, by performing the defibration process step, after treating the resulting fine fibrous cellulose-containing slurry with an ion exchange resin, by determining the change in electrical conductivity while adding an aqueous sodium hydroxide solution, The amount introduced was measured.
In the treatment with an ion exchange resin, 1/10 by volume of a strongly acidic ion exchange resin (Amberjet 1024; Organo Corporation, conditioned) is added to a slurry containing 0.2% by mass of fine fibrous cellulose and shaken for 1 hour. Processed. Thereafter, the mixture was poured onto a mesh having an opening of 90 μm to separate the resin and the slurry. In the titration using an alkali, the change in the value of electrical conductivity exhibited by the slurry was measured while adding a 0.1 N sodium hydroxide aqueous solution to the fine fibrous cellulose-containing slurry after ion exchange.

In this conductivity titration, the curve shown in FIG. 1 is given when alkali is added. Initially, the electrical conductivity rapidly decreases (hereinafter referred to as “first region”). Thereafter, the conductivity starts to increase slightly (hereinafter referred to as “second region”). Thereafter, the conductivity increment increases (hereinafter referred to as “third region”). That is, three areas appear. Among these, the amount of alkali required in the first region is equal to the amount of strongly acidic groups in the slurry used for titration, and the amount of alkali required in the second region is the amount of weakly acidic groups in the slurry used for titration. Will be equal.
The alkali amount (mmol) required in the first region of the curve shown in FIG. 1 was divided by the solid content (g) in the titration target slurry to obtain a phosphate group introduction amount (mmol / g).

<How to determine the reaction rate>
The reaction rate was measured for each of Examples A-1 to A-3 and Comparative Example A-1 as follows. First, phosphate groups were introduced in the same manner as in the phosphorylation reaction step described above except that the heat drying time was 60 minutes. At that time, the phosphate group introduction amount was measured every 10 minutes from 10 minutes to 60 minutes. The vertical axis is the phosphate group introduction amount (mmol / g), the horizontal axis is the reaction time (min), and the obtained data is plotted on a graph. An approximate line was created from the plotted graph, and the slope of the approximate line was defined as the reaction rate a (mmol / g · min).

  As can be seen from Table 1, in the examples, the heating and drying time was shorter than in the comparative example, but a sufficient amount of phosphate groups had been introduced. Moreover, the phosphorylation reaction rate was also fast. That is, in the Example, it turned out that the manufacturing efficiency of phosphorylated fine fibrous cellulose can be improved more effectively.

(Example B-1)
As a cellulose-containing material, a pulp sheet made of Oji Paper (solid content: 93% by mass, basis weight of 208 g / m ² sheet, Canadian standard freeness (CSF) 700 ml which is disaggregated and measured according to JIS P 8121) The fluffed pulp was obtained and used as a raw material. 100 parts by mass of fluffed pulp (absolute dry mass), 167 parts by mass of normal phosphoric acid, 1000 parts by mass of urea (manufactured by Kanto Chemical Co., Ltd.), 1000 parts by mass of N, N-dimethylformamide (DMF) (manufactured by Kanto Chemical Co., Ltd.) In addition to the round bottom flask, it was heated and refluxed at 150 ° C. for 15 minutes to introduce phosphate groups into the cellulose fibers in the pulp, thereby obtaining a phosphorylated cellulose-containing product C. Thereafter, a defibrated pulp slurry (fine fibrous cellulose-containing slurry) was obtained in the same manner as in Example A-1.

(Example B-2)
A defibrated pulp slurry (fine fibrous cellulose-containing slurry) was obtained in the same manner as in Example B-1, except that 196 parts by mass of 85% phosphoric acid was used instead of 167 parts by mass of regular phosphoric acid.

(Example B-3)
A defibrated pulp slurry (fine fibrous cellulose-containing slurry) was prepared in the same manner as in Example B-1, except that dimethyl sulfoxide (DMSO) (manufactured by Kanto Chemical Co., Inc.) was used instead of N, N-dimethylformamide. Obtained.

(Example B-4)
A defibrated pulp slurry (a slurry containing fine fibrous cellulose) was obtained in the same manner as in Example B-1, except that urea was used instead of N, N-dimethylformamide.

(Comparative Example B-1)
Example B-1 except that 1000 parts by mass of N, N-dimethylformamide and 1000 parts by mass of urea were replaced by 433 parts by mass of N, N-dimethylformamide, 433 parts by mass of urea, and 1133 parts by mass of ion-exchanged water. Thus, a defibrated pulp slurry (fine fibrous cellulose-containing slurry) was obtained.

(Comparative Example B-2)
A defibrated pulp slurry (a slurry containing fine fibrous cellulose) was obtained in the same manner as in Comparative Example A-1.

(Evaluation)
The fluffed pulp (cellulose-containing material before phosphorylation) used in the phosphorylation reaction step obtained in Examples B-1 to B-4 and Comparative Examples B-1 and B-2, obtained after the washing alkali treatment step The obtained phosphorylated cellulose fiber (phosphorylated cellulose-containing material) was tested, and the specific viscosity and the degree of polymerization were measured by the methods described later. Further, the defibrated pulp slurry after the mechanical treatment was tested, and the phosphate group introduction amount was measured by the same method as described in <Measurement of phosphate group introduction amount (phosphate group amount)> described above. Further, the defibrated pulp slurry after the mechanical treatment was tested and the viscosity was measured by the method described later.

<Measurement of specific viscosity and degree of polymerization>
Specific viscosity and degree of polymerization were measured according to Tappi T230. That is, the viscosity measured by dispersing the pre-phosphorylated cellulose-containing material or phosphorylated cellulose-containing material to be measured in a dispersion medium (referred to as η ₁ ), and the blank viscosity measured as a dispersion medium alone (referred to as η ₀ ). After measurement, specific viscosity (η _sp ) and intrinsic viscosity ([η]) were measured according to the following formula.
η _sp = (η ₁ / η ₀ ) -1
[Η] = η _sp /(c(1+0.28×η _sp ))
Here, c in a formula shows the density | concentration of the cellulose containing material or phosphorylated cellulose containing material at the time of a viscosity measurement.
Furthermore, the degree of polymerization (DP) in the present invention was calculated from the following formula.
DP = 1.75 × [η]
Since this degree of polymerization is an average degree of polymerization measured by the viscosity method, it may be referred to as “viscosity average degree of polymerization”.

<Measurement of viscosity of slurry containing fine fibrous cellulose>
The viscosity of the fine fibrous cellulose-containing slurry was diluted with a disperser at 1500 rpm for 5 minutes after being diluted so that the solid content concentration of the fine fibrous cellulose-containing slurry was 0.4% by mass. The viscosity of the obtained slurry was measured using a B-type viscometer (manufactured by BLOOKFIELD, analog viscometer T-LVT). The measurement conditions were 3 rpm and a liquid temperature of 25 ° C.

  As can be seen from Table 2, in the examples, the specific viscosity of the phosphorylated cellulose fiber-containing slurry after the phosphorylation reaction was high, and it was found that a high solution viscosity could be expressed even after the fine fibrous cellulose was obtained.

Claims (11)

A method for producing phosphorylated cellulose fibers comprising a step of phosphorylating cellulose fibers,
A method for producing phosphorylated cellulose fibers, wherein the initial moisture content of the reaction system is less than 40% by mass.   The said phosphorylating process is a manufacturing method of the phosphorylated cellulose fiber of Claim 1 including the process of mixing the said cellulose fiber, an organic solvent, and a phosphorylating agent.   The organic solvent is dimethylformamide (DMF), dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), aniline, pyridine, quinoline, lutidine, acetonitrile, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), dioxane and urea. The manufacturing method of the phosphorylated cellulose fiber of Claim 2 containing at least 1 sort (s) chosen.   The said phosphorylating agent is a manufacturing method of the phosphorylated cellulose fiber of Claim 2 or 3 containing at least 1 sort (s) chosen from dehydration condensation phosphoric acid, anhydrous phosphoric acid, and phosphoric acid. The phosphorylating step includes a heating step,
5. The phosphorylation reaction rate from the start of heating to the lapse of 60 minutes when heated at 140 ° C. in the heating step is 0.018 mmol / g · min or more. 5. The manufacturing method of the phosphorylated cellulose fiber as described in any one of.   The specific viscosity measured according to Tappi T230 of the cellulose-containing material including the cellulose fiber before undergoing the phosphorylation step is V1, and according to Tappi T230 of the cellulose-containing material including the cellulose fiber obtained in the phosphorylation step. The method for producing phosphorylated cellulose fibers according to any one of claims 1 to 5, wherein the value of V2 / V1 is 0.74 or more when the measured specific viscosity is V2.   The specific viscosity measured according to Tappi T230 of the cellulose containing material containing the cellulose fiber obtained at the said phosphorylation process is 8.0 or more, The phosphorylated cellulose fiber of any one of Claims 1-6 Manufacturing method. A cellulose-containing material containing cellulose fibers having a fiber width of 1000 nm or less,
The viscosity of the slurry obtained by diluting the cellulose-containing material with water so that the solid content concentration is 0.4% by mass, measured with a B-type viscometer under conditions of 3 rpm and a liquid temperature of 25 ° C., is 14500 mPa · Cellulose-containing material that is s or more.   A cellulose-containing product comprising cellulose fibers having a phosphate group of 0.1 mmol / g or more and having a specific viscosity of 8.0 or more measured according to Tappi T230.   The cellulose-containing material according to claim 9, wherein the degree of polymerization obtained by measurement according to Tappi T230 is 870 or more.   The cellulose-containing material according to claim 9 or 10, comprising an organic solvent component.

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